Alternaria solani is a fungus that causes early blight disease in solanaceous crops like tomatoes and potatoes. It produces brown leaf spots with concentric rings and can defoliate plants under favorable warm, wet conditions. The disease cycle involves the fungus surviving in soil or infected debris and spreading via wind-blown conidia that infect leaves when wet and favorable temperatures between 15-29°C occur.
2. PGP COLLEGE OF AGRICULTURAL SCIENCE
(Affiliated to TamilNadu agricultural university,Coimbatore-3)
Senthamangalam Rd, Palani Nagar, Namakkal -637405
SYMPTOMS AND LIFE CYCLE OF
Alternaria solani
STUDENT COURSE TEACHER
Ms.Malathi.P Mr.M.Krishnamoorthi
ID.No.2019024051 Assistant professor
PGP college of agricultural sciences
Course Associate
Ms.T.Suganya
3. INTRODUCTION
• Alternaria solani
• Causative agents - early blight in solanum
species
• The pathogen produces distinctive “bullseye”
patterned leaf spots and can also cause stem
lesions and fruit rot on tomato and tuber
blight on potato.
4. Alternaria
• It is multicellular
pigmented spores are
produced in chains or
in branching fashion
9. SYMPTOMS
• Foliar symptoms of Alternaria solani - oldest
leaves and smart as small lesions that are
brown to black on color.
• These leaf spots - concentric rings
• Both the area around the leaf spot and the
entire leaf may become yellow or chlorotic.
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15. • Under favorable conditions (e.g., warm weather
with short or abundant dews) - significant
defoliation of lower leaves , leading to sunscald of
the fruit.
• Stem lesions - dark, slightly sunken and
concentric in shape.
• Fruits spots are similar leaves – brown with dark
concentric circes.
• Mature lesions - a black, velvety mass of fungal
spores
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17. SYSTEMATIC CLASSIFICATION /
TAXONOMIC POSITION
• Domain : Eukarya
• Kingdom : Fungi
• Phylum : Ascomycota
• Class : Dothediomycetes
• Order : Pleosporales
• Family : Pleosporaceae
• Genus : Alternaria
• Species : solani
18. PATHOGENIC CHARACTER
• The mycelium - septate and branched, hyaline
in the beginning and later becomes darker in
color
• The conidia - 12-20 × 120-296 µm
• Conidia - 9-11 transverse septa (cross walls).
• Conidiophores are short and produces an
obclavate of muriform shaped conidia with
horizontal and vertical septation and it is
pointed at distal end.
20. MODE OF REPRODUCTION
• Alternarias - no sexual or perfect stage.
• The multiply asexually - sporulation.
• asexual spores - exogenously are the conidia.
• The conidia are produced at the tips of
ordinary hyphae which are comparatively
short and dark coloured .
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23. • The conidia - large, dark coloured, several
celled and beaked.
• The number of cells - 8-14 or even more .
• The component cells occur packed in
muniform, conidal masses.
• The septa dividing the spore into cell and both
transverse and vertical and their number is
not fixed.
28. • The fungus can survive in soil and in infested
crop and weed residues.
• It may be seed-borne and carried by wind,
water, insects, workers and farm equipment.
• The spores that land on tomato plants will
germinate and infect the leaves when they are
wet.
29. • Spores enter - leaf, steam or fruit.
• The fungus more active - mild to warm
temperature and wet weather.
• The disease worse during - rainy seasons.
• Early blight is most severe on plants stressed
by a heavy fruit load, nematode attack, or low
nitrogen fertility.
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31. FAVOURABLE WEATHER CONDITIONS
• Maximum temperature of 15-29°C
• Minimum temperature of 4-12°C
• Average relative humidity >60%
• RH I (Morning)>76%
• RH II (Afternoon)>25%
32. MANAGEMENT ASPECTS
CULTURAL CONTROL
Clear infected debris from field to reduce
inoculum from the next year.
Rotate to a non-solanaceous crop for atleast
three years.
Removal and destruction of infected plant
debris should be done because the spores
lying in the soil are the primary source of
infection.
33. CHEMICAL CONTROL
Very early spraying with zineb or captan 0.2%
and repeating it for every 15-20 days gives
effective control.
34. CONCLUSION
• Moreover to determine the levels of genetic
varation of alternaria spp. Is important to
know the population structure and migration
structure of the pathogen.
35. • Early blight of tomato,dark black and slightly
sunken, sunscald of fruit.
• Picture courtesy : J.B.Jones , T.A.Zitter ,
M.T.Momol, and S.A.Miller , Tomato diseases.
36. • Conidia of alternaria solani , blue brightfield
conidia, fungus infection.
• Picture courtesy : nature picture library
conidia